A wireless device (e.g., a cellular phone or a smartphone) in a wireless communication system may include a radio frequency (RF) transceiver to transmit and receive data for two-way communication. A mobile RF transceiver may include a transmit section for data transmission and a receive section for data reception. For data transmission, the transmit section may modulate an RF carrier signal with data to obtain a modulated RF signal, amplify the modulated RF signal to obtain an amplified RF signal having the proper output power level, and transmit the amplified RF signal via an antenna to a base station. For data reception, the receive section may obtain a received RF signal via the antenna and may amplify and process the received RF signal to recover data sent by the base station.
The transmit section of the mobile RF transceiver may amplify and transmit a communication signal. The transmit section may include one or more circuits for amplifying and transmitting the communication signal. The amplifier circuits may include one or more amplifier stages that may have one or more driver stages and one or more power amplifier stages. Each of the amplifier stages includes one or more transistors configured in various ways to amplify the communication signal. The transistors configured to amplify the communication signal are generally selected to operate at substantially higher frequencies for supporting communication enhancements.
Gallium Arsenide (GaAs) heterojunction bipolar transistors (HBTs) are an important technology for amplifiers, such as power amplifiers (PAs). The integrity of interconnect layers (e.g., metallization one layer (M1), metallization two layer (M2), metallization x layer (Mx), etc.) in GaAs HBTs is important for PA reliability due to high power and high junction temperature of HBTs. Conventional HBTs exhibit cracking and/or forming of seams, which results in undesired conductivity reduction and/or failure of the HBT. Therefore, there is a desire for HBTs that overcome these deficiencies.